Fuel tanks

ABSTRACT

A bunded tank is provided which includes inner and outer walls, wherein the inner and outer walls, when the tank is viewed in transverse cross-section, define a substantially rectangular shape, wherein each inner and outer wall has an at least partially convex profile, wherein adjacent sides of the inner and outer walls are connected by rounded corners, and wherein the inner and outer walls are arranged with respect to one another to create an inner tank and an outer tank.

STATEMENT OF CORRESPONDING APPLICATIONS

This application is based on the Provisional specification filed inrelation to Australian Patent Application Number 2010903302, the entirecontents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to improvements in and relating to fueltanks. More specifically to improvements in bunded fuel storage tanks.

BACKGROUND ART

A large number of styles and configurations of fuel tanks exist. Onerequirement of fuel tanks is that they include an outer wall, orenclosure, to capture spillage in the event of rupture or leaking froman inner enclosure. This encapsulation is referred to in the industry asbunding. It should be understood that bunding does not involve completeencapsulation of an inner enclosure, rather the outer enclosure shouldbe capable of capturing any spilt fluid. For example, a bunded enclosurecould comprise a single layer inner tank, around which is built a walledand open topped structure, such as a surrounding wall.

The size and/or shape of a tank can be dictated by a number of differentcriteria depending upon where the tank is to be located, or whether itis to be built in situ, or transported to its final location.

Tanks which require transporting, whilst not restricted to anyparticular shape or configuration, are typically kept within the boundsof a standard shipping container's dimensions. The reason for thislimitation is to allow both ease of transport on a standard containertransport or (vessel or vehicle) and also to minimise costs.Transportation of freight is typically based on containerised rates, orthe volumetric equivalence of a standard rectangular shipping crate.There are five common standard lengths of container, 20-ft (6.1 m),40-ft (12.2 m), 45-ft (13.7 m), 48-ft (14.6 m), and 53-ft (16.2 m),container width is standard across all lengths, at 8-ft (2.44 m).

In order to maintain structural integrity (rigidity) of a tank in:

-   -   an empty form;    -   a transport ready form; and    -   a fully laden fuel storage state,        the fuel tank body is either shaped to provide the required        structural integrity, or external or internal reinforcement is        added to the tank to provide additional strength.

Both methods of adding external, or internal, reinforcement and/orconfiguring the shape of the tank, result in significant loss incapacity of the tank. This can best be explained with reference to thefollowing prior art tank embodiments.

Rectangular Tanks with External or Internal Reinforcing:

It will be appreciated by a person skilled in the art of engineeringthat any weight applied to the centre of a flat sheet will result in aforce acting to pull the sheet in on itself, or conversely bulge outwardif the flat sided tank is subjected to an internal pressure such as fromfuel stored therein. Due to these structural limitations, flat sidedtanks require substantial reinforcing to provide the requisite strength.If the tank is limited to the dimensions of a containerised footprint,the dimensions of any external, or internal, reinforcing will subtractfrom the available capacity of the tank. A further disadvantage of flatwalled fuel tanks is the tendency for water and debris to pool orcollect on the top of the tank. This is undesirable as it can result incorrosion and premature failure of the tank, resulting in contaminationand further cost.

Round or Oval Tank Shapes:

Both round and oval tanks provide substantial advantages overrectangular tanks in terms of structural integrity and also in theability to naturally shed any water or debris from the tank. Howeverthese advantages come at the expense of capacity. Per unit volume around tank is poor value when compared to rectangular tanks with respectto the same containerised volumetric area.

All references, including any patents or patent applications cited inthis specification are hereby incorporated by reference. No admission ismade that any reference constitutes prior art. The discussion of thereferences states what their authors assert, and the applicants reservethe right to challenge the accuracy and pertinency of the citeddocuments. It will be clearly understood that, although a number ofprior art publications are referred to herein, this reference does notconstitute an admission that any of these documents form part of thecommon general knowledge in the art, in New Zealand or in any othercountry.

Throughout this specification, the word “comprise”, or variationsthereof such as “comprises” or “comprising”, will be understood to implythe inclusion of a stated element, integer or step, or group of elementsintegers or steps, but not the exclusion of any other element, integeror step, or group of elements, integers or steps.

It is an object of the present invention to address the foregoingproblems or at least to provide the public with a useful choice.

Further aspects and advantages of the present invention will becomeapparent from the ensuing description which is given by way of exampleonly.

DISCLOSURE OF THE INVENTION

According to one aspect of the present invention there is provided abunded tank which includes inner and outer walls (“the walls”),

wherein the inner and outer walls, when the tank is viewed in transversecross-section, define a substantially rectangular shape (SRS) whereineach inner or outer wall has an at least partially convex profile,

wherein adjacent sides of the inner and/or outer walls are connected byrounded corners, and

wherein the inner and outer walls are arranged with respect to oneanother to create an inner tank and an outer tank.

As used herein the term ‘wall’ refers to a material layer or surfacewhich forms a barrier.

A wall may be configured as a continuous surface which may enclose aspace.

Preferably the inner and outer walls of the bunded tank may eachrespectively have a cross sectional profile which includes two lines ofsymmetry.

In especially preferred embodiments the two lines of symmetry are avertical line of symmetry and a horizontal line of symmetry. It will beappreciated that the outer tank shares at least one wall with the innertank, therefore the respective symmetry of the inner and outer tankshould be understood to each include the shared inner/outer wall.Collectively the inner and outer wall share a single line of symmetrywhich, in preferred embodiments, is a vertical line.

Bunded tanks are known in the art of hazardous liquid storage as beingany tank having a inner and an outer wall. The inner wall defines thearea of the tank that contains the stored liquid. The outer wallprovides redundancy in the event that the inner wall becomes damaged orotherwise fails to contain the liquid therein. In the present inventionthe inner and outer walls are adjacent each other and may be in directcontact, or separated by a gap, or separated by insulation, between theinner and outer walls.

In preferred embodiments the inner wall is formed from steel. Howeverthe inner wall may be any suitably corrosion resistant material.

In some embodiments the inner wall may be impervious to the fluidcontained therein, but may provide no structural support, for example abladder.

In some embodiments the inner wall may be a coating on the inside of theouter wall.

In some preferred embodiments the inner wall is of a seamlessconstruction.

In other preferred embodiments the inner wall may be identical instructure to the outer wall.

In preferred embodiments the outer wall is formed from steel. In otherembodiments the outer wall may be a composite material.

In preferred embodiments the outer wall is made by way of one or moresections, such as:

-   -   at least one centre section; and    -   at least two end cap sections.

It will be appreciated that the SRS of the outer wall forming the bundedtank provides a single integrated structure capable of substantiallymaintaining its shape during transportation and storage of fluidtherein.

In preferred embodiments the SRS outer wall is substantially monocoque.

In some preferred embodiments the tank may include one or more plugwelds or other joins between the inner and outer walls at one or morelocations along the length of the tank. This is particularlyadvantageous for embodiments which are 12.2 m or greater in length. Theplug welds prevent the inner walls from bulging under pressure andmaking contact with the outer walls.

In preferred embodiments the end caps of the tank include a partialoutwardly convex curved profile.

In preferred embodiments the tank includes isoblock connectors or thelike on the lower side of the tank.

In preferred embodiments the isoblock connectors or the like are locatedsymmetrically on the bottom of the tank.

In some preferred embodiments isoblock connectors or the like arelocated on the upper side of the tank.

In preferred embodiments the isoblock connectors are located on theouter corners of the tank. It will be appreciated that the isoblockconnectors provide a connection point to which lifting chains or stropscan be attached. A person skilled in the art would understand that theisoblock connection points will be positioned evenly about the centre ofgravity of the tank; such that the tank is evenly supported when beinglifted at the isoblock connection points.

In preferred embodiments the isoblock connectors are located at the endsof the tank. However it will be apparent to a person skilled in the artthat the isoblock connectors could be located at any position on thetank that allows balanced lifting of the tank.

In some preferred embodiments the tank includes one or more lowersupport members.

In one preferred embodiment lower support members are in the form of twoparallel supports substantially running the length of the tank.

In some preferred embodiments the lower support members comprise aplurality of supports running in either a longitudinal direction, atransverse direction or a combination of longitudinal and transversedirections. The configuration of the lower support members shouldtherefore not be seen as being limiting. The purpose of the lowersupport members is to distribute the weight of the tank and the tankscontents into a support platform such as the ground or a concrete slab.It will be apparent to a person skilled in the art that:

-   -   the number of supports;    -   the spacing of the supports; and    -   the shape or configuration of the supports, will be defined by:    -   the resiliency of the tank structure; and    -   the resiliency of the support platform.

In preferred embodiments the isoblock connectors may be integral withthe lower support members.

In other embodiments the isoblock connectors may be attached to the tankby way of support struts or the like.

According to another aspect of the present invention there is provided amethod of constructing a bunded fuel tank having inner and outer walls,

wherein each inner or outer wall has an at least partially convexprofile; and

wherein adjacent sides of the inner and/or outer walls are connected byrounded corners, and

wherein the inner and outer walls are arranged with respect to oneanother to create an inner tank and an outer tank, the method includingthe steps of:

-   -   a) pre-forming one or more standard sheets of material into one        or more SRS sections for the inner walls;    -   b) forming one or more standard sheets of material into end caps        for the inner wall;    -   c) pre-forming one or more standard sheets of material into one        or more SRS sections for the outer wall;    -   d) forming one or more standard sheets of material into end caps        for the outer wall;    -   e) joining the one or more SRS sections forming the inner wall        together to form a single inner SRS tube;    -   f) joining the one or more SRS sections forming the outer wall        together to form a single outer SRS tube forming an enclosure        about at least a section of the inner SRS tube;    -   g) joining the end caps for the inner wall to the inner SRS        tube;    -   h) joining the end caps for the outer wall to the outer SRS        tube; and    -   i) joining the one or more lower support members and integrated        isoblock connectors to the lower surface of the SRS tank.

In preferred embodiments the section of the inner tank that is enclosedby the outer SRS tube in method step f) comprises substantially threesides and both ends of the inner SRS tube.

In preferred embodiments the method of constructing a fuel tank includesthe further step j) wherein one or more apertures are cut through thesection of the inner SRS tube that is not enclosed by the outer SRStube. It is preferred not to cut through both the outer and inner SRSlayers as this would result in introduction of a weakness in the bund.Therefore access to the tank contents is typically configured throughaccess ports cut in the upper surface of the tank.

In preferred embodiments the side of the inner SRS layer that is notenclosed by the outer SRS tube is the upper surface of the tank.

In preferred embodiments the sheet material is steel.

In preferred embodiments the sheets of steel are joined by welding.

According to another aspect of the present invention there is provided abunded tank substantially as described above wherein the tank includesat least two longitudinally extending support structures on theunderside of the floor region.

Preferred embodiments of the bunded tank substantially as describedabove may have one or more of the following advantages:

-   -   the tank is self supporting whether it is filled, or not filled,        with liquid;    -   the tank is capable of having isoblock connection points        attached to the top of the tank and upon the support structures        which may allow the tanks to be more easily handled for shipping        and transportation purposes;    -   the dimensions and SRS of the tank provides comparable        volumetric capacity to a standard shipping container;    -   the configuration of the tank provides a high volume, aesthetic        relocatable, fuel tank; and    -   the tank may be permanently sited as the convex sides and top do        not allow water and debris to collect on the tank.

BRIEF DESCRIPTION OF DRAWINGS

Further aspects of the present invention will become apparent from thefollowing description which is given by way of example only and withreference to the accompanying drawings in which:

FIG. 1 a an isometric drawing showing a bunded tank according to onepreferred embodiment of the present invention;

FIG. 1 b shows a transverse cross section of the bunded tank of FIG. 1a;

FIG. 2 a an isometric drawing showing the inner wall middle section ofthe bunded tank shown in FIG. 1 a;

FIG. 2 b an isometric drawing showing the inner wall end section of thebunded tank shown in FIG. 1 a;

FIG. 2 c an isometric drawing showing the inner wall end cap of thebunded tank shown in FIG. 1 a;

FIG. 3 a an isometric drawing showing the outer wall middle section ofthe bunded tank shown in FIG. 1 a;

FIG. 3 b an isometric drawing showing the outer wall end section of thebunded tank shown in FIG. 1 a;

FIG. 3 c an isometric drawing showing the outer wall end cap of thebunded tank shown in FIG. 1 a;

FIG. 4 an isometric view of an inner tank of the bunded tank shown inFIG. 1 a;

FIG. 5 an isometric view of an outer tank of the bunded tank of FIG. 1a; and

FIG. 6 shows a further embodiment of a bunded tank.

BEST MODES FOR CARRYING OUT THE INVENTION

With respect to FIGS. 1 a, 1 b and 6 there is shown a bunded tank, asgenerally indicated by arrow 1. The bunded tank 1 has an inner steelsheet wall 2 (of which only the top is visible) and an outer steel sheetwall 3. The relationship of the inner wall 2 and the outer wall 3 areillustrated in the transverse cross-sectional profile of FIG. 1 b,wherein the inner wall 2 is enclosed by the outer wall 3 onsubstantially three sides. The uppermost surface 202 of the inner wall 2forms both an inner wall 2 and at least a portion of an outer wall 3 ofthe tank.

With respect to FIGS. 2 a-2 c the various components which make up theinner wall 2 are shown. The inner wall 2 of the tank 1 has 3 SRSsections in the form of strakes, shown in FIGS. 2 a-2 c which include:

-   -   an inner wall middle section 2 a; and    -   a first and second inner wall end sections 2 b.

The inner wall 2 also includes two end caps 2 c. The orientation inwhich inner wall 2, sections 2 a, 2 b and 2 c are connected together isshown in FIG. 4. It will be appreciated that the inner wall 2 sectionscould be attached to one another in a number of ways without departingfrom the scope of the invention. However, in the embodiment shown thesections are welded together. The inner wall 2 of FIG. 4 also includesan access port in the top surface thereof over which is bolted a hatchplate 100. Also visible shown in FIG. 4 are overhanging lips 101 foundin inner wall end sections 2 b.

With respect to FIGS. 3 a-3 c the various components which make up oneportion of the outer wall 3 are shown. It will be appreciated that theuppermost surface 202 of the inner wall 2 also forms part of the outerwall. However, for the purposes of clarity the outer wall is describedonly in terms of the components that only comprise outer walls. Theouter wall 3 of the tank includes 3 SRS sections in the form of strakes,shown in FIGS. 3 a-3 c which comprise:

-   -   an outer wall middle section 3 a; and    -   a first and second outer wall end sections 3 b.

The outer wall 3 also includes two end caps 3 c. The manner in whichouter wall 3, sections 3 a and 3 b are connected together is shown inFIG. 5. It will be apparent to a person skilled in the art that the opentub shape excluding the inner tank 2 as depicted in FIG. 5 would neverexist in reality as the inner tank would always be located inside theouter tank 3 prior to completion of welding. It will be appreciated thatthe outer wall sections could be attached to one another in a number ofways without departing from the scope of the invention. However in theembodiment shown the sections are welded together.

Further to the welding of the individual sections of the inner 2 andouter 3 walls of the tank 1, the upper most surface 202 of the innerwall 2 is welded to the outer wall 3 along the edges 201 of the open topof the tub shape shown in FIG. 5. It will be appreciated that the innertank 2 shown in FIG. 4 fits entirely within the outer open topped tankof FIG. 5 and welding in this manner effectively suspends the inner tank2 within the outer tank 3. This is illustrated in the transverse crosssection of FIG. 1 b where a gap 200 can be seen between substantially 3sides of the inner 2 and outer 3 walls of the tank 1. Whilst not shownin the drawings, it will be appreciated that a similar gap will existbetween the inner end wall 2 c and outer end wall 3 c of the tank.Because the inner end walls 2 c are spaced apart from the outer endwalls 3 c, if an overhanging lip 101, or the like, is not included a gapwill be left at the top of the tank between the inner 2 c and outer 3 cend walls. Thus the lips 101 both cover the gap that would otherwise beleft and also provide a greater weld area by which to attach the inner 2c and outer 3 c tanks.

As most clearly shown in the transverse cross section of FIG. 1 b, thebody of the tank 1 is substantially rectangular in form, bounded by fourdistinct sides 4, each opposed side 4 of the inner 2 and outer 3 wallsis further defined by a partial convex curved profile 4 a. Adjacentsides 4 of the inner 2 and outer 3 walls are connected by roundedcorners 4 b along adjacent edges 4 c of the partial convex curvedprofile 4 a.

The tank 1 is constructed in a number of SRS tube sections. For thepurposes of clarity, the tank 1 has been described in terms of onepreferred length only, comprising 3 SRS tube sections. It will beapparent to a person skilled in the art that the length of the tank 1can be altered by using more or less of the SRS tube sections.

As shown in FIGS. 1 and 6, the tank 1 also includes longitudinallyextending support structures 7 welded to the bottom of the tank 1. Thelongitudinally extending support structures 7 include integratedisoblock connection points 8, of which only 3 are visible.

FIG. 1 a shows an embodiment in which welded to the upper surface of thetank 1 are support struts 10, into which upper isoblock connectors 9,are integrated.

Aspects of the present invention have been described by way of exampleonly and it should be appreciated that modifications and additions maybe made thereto without departing from the scope thereof as defined inthe appended claims.

1. A bunded tank which includes inner and outer walls, comprising: theinner and outer walls, when the tank is viewed in transversecross-section, define a substantially rectangular shape wherein eachinner and outer wall has an at least partially convex profile: adjacentsides of the inner and outer walls are connected by rounded corners; theinner and outer walls are arranged with respect to one another to createan inner tank and an outer tank; and the SRS of the outer wall issubstantially monocoque.
 2. The bunded tank as claimed in claim 1,wherein the outer wall is made by way of one or more sections,including: at least one centre section; and at least two end capsections.
 3. The bunded tank of claim 1, wherein the tank includes oneor more plug welds or other joins between the inner and outer walls atone or more locations along the length of the tank.
 4. The bunded tankof claim 2, wherein the end cap sections of the tank also include an atleast partially convex profile.
 5. The bunded tank of claim 1, whereinthe tank includes one or more isoblock connectors on a lower side of thetank.
 6. The bunded tank of claim 5, wherein the one or more isoblockconnectors are located symmetrically on the bottom of the tank.
 7. Thebunded tank of claim 5, wherein one or more isoblock connectors arelocated on an upper side of the tank.
 8. The bunded tank of claim 5,wherein one or more of the isoblock connectors are located on outercorners of the tank.
 9. The bunded tank of claim 5, wherein one or moreof the isoblock connectors are located at the ends of the tank.
 10. Thebunded tank of claim 5, wherein one or more of the isoblock connectorsare attached to the tank by way of support struts or the like.
 11. Thebunded tank of claim 1, wherein the tank includes one or more lowersupport members.
 12. The bunded tank of claim 11, wherein the lowersupport members are in the form of two parallel supports runningsubstantially the length of the tank.
 13. The bunded tank of claim 12,wherein the lower support members comprise a plurality of supportsrunning in either a longitudinal, a transverse direction or acombination of longitudinal and transverse directions.
 14. The bundedtank as claimed in claim 11, wherein lower isoblock connectors areintegral with the lower support members.
 15. A method of constructing abunded fuel tank having inner and outer walls, wherein each inner orouter wall has an at least partially convex profile; wherein adjacentsides of the inner and/or outer walls are connected by rounded corners;and wherein the inner and outer walls are arranged with respect to oneanother to create an inner tank and an outer tank, the methodcomprising: a) pre-forming one or more standard sheets of material intoone or more SRS sections for the inner walls; b) forming one or morestandard sheets of material into end caps for the inner wall; c)pre-forming one or more standard sheets of material into one or more SRSsections for the outer wall; d) forming one or more standard sheets ofmaterial into end caps for the outer wall; e) joining the one or moreSRS sections forming the inner wall together to form a single inner SRStube; f) joining the one or more SRS sections forming the outer walltogether to form a single outer SRS tube forming an enclosure about atleast a portion of the inner SRS tube; g) joining the end caps for theinner wall to the inner SRS tube; h) joining the end caps for the outerwall to the outer SRS tube; and i) joining one or more lower supportmembers to the lower surface of the SRS tank.
 16. The method of claim 15further including the step of attaching one or more isoblock connectorsto the lower supports of the SRS tank.
 17. The method of claim 15further characterised in that the portion of the inner tank that isenclosed by the outer SRS tube in method step f) comprises substantiallythree sides and both ends of the inner SRS tube.
 18. The method ofconstructing a fuel tank as claimed in claim 15, including: j) formingone or more apertures through the portion of the inner SRS tube that isnot enclosed by the outer SRS tube.
 19. The method of claim 15 whereinthe sheet material is plate steel.
 20. The method of claim 19 whereinjoining the plate steel sheets includes welding.
 21. A method ofconstructing a bunded fuel tank having inner and outer walls,comprising: forming inner and outer walls which are SRS when viewed intransverse cross section; each inner and outer wall has an at leastpartially convex profile; adjacent sides of the inner and outer wallsare connected by rounded corners; and the inner and outer walls arearranged with respect to one another to create an inner tank and anouter tank.
 22. (canceled)
 23. (canceled)